Mortality and incidence of tumours among ferrochromium workers

Our plain-English summary of Mortality and incidence of tumours among ferrochromium workers, by G. Axelsson, R. Rylander, A. Schmidt (British Journal of Industrial Medicine, 1980).

The study

• Authors: G. Axelsson, R. Rylander, A. Schmidt
• Journal: British Journal of Industrial Medicine
• Published: 1980;37(2):121-7
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

ABSTRACT An investigation was carried out to determine the cause of death and the incidence of tumours among 1932 workers in a ferrochromium plant in Sweden. The workers had been exposed mainly to metallic and trivalent chromium (Cr3+); hexavalent chromium (Cr6+) was also present in certain working operations. The population was defined as all men employed at the plant for at least one year during 1930-75, and were classified according to their occupation within the industry. The causes of death were initially obtained from parish registers. For deaths occuring between 1951 and 1975, death certificates were collected from the National Central Bureau of Statistics. Data on the incidence of cancer during 1958-75 were obtained from the Swedish National Cancer Registry. Expected death rates and incidence of tumours were calculated, based on the rates for the county in which the factory was situated. The total number of deaths from tumours was less than expected (69 versus 76·7). Five cases of respiratory cancer were found, against an expected 7·2. Among maintenance workers, an increased death rate from all tumours and an increased number of respiratory tumours were found. Two of the latter were mesotheliomas and could be connected with asbestos exposure. No increase was found for respiratory tumours among the heavily exposed workers at the arc-furnaces; one case of mesothelioma was found in this group.

In plain English

This retrospective cohort study examined men employed for at least one year during 1930-75 at a ferrochromium plant in Trollhättan, Sweden. They were exposed mainly to metallic and trivalent chromium, with hexavalent chromium in some operations. Asbestos-containing textiles, plates and asbestos-isolated tubes had also been used at the plant. Deaths during 1951-75 (1876 men) and cancers diagnosed during 1958-75 (1823 men) were compared with expected numbers based on county rates. Overall, 69 men died of tumours against 76.7 expected, and 5 died of respiratory tumours against 7.2 expected. Among maintenance workers, 4 respiratory tumours were diagnosed against 1.0 expected, and two of these were pleural mesotheliomas. One further mesothelioma occurred among arc-furnace workers, whose respiratory tumours were not increased (2 against 2.1 expected). The authors considered the mesotheliomas probably related to asbestos handling. They concluded that the study could not show an increased death rate or cancer incidence, and that it is reasonable to believe the respiratory tumour risk from inhaled trivalent chromium is considerably less than from chromates. Smoking data were unavailable, and exposure levels were approximate.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective cohort study of mortality (1951-75) and cancer incidence (1958-75), with observed numbers compared against expected numbers calculated from county rates
• Who was studied: 1932 men employed for at least one year between 1 January 1930 and 31 December 1975 at a ferrochromium plant in Trollhättan, Sweden. The mortality analysis covered the 1876 men alive on 1 January 1951. The cancer incidence analysis covered the 1823 men alive on 1 January 1958. Workers were grouped by work site: arc-furnaces; transport, metal grinding and sampling; maintenance; and office or storage areas.
• Exposure: Mainly metallic and trivalent chromium, with hexavalent chromium in some operations; exposure levels were estimated, not measured. Asbestos-containing materials (textiles, plates, asbestos-isolated tubes) had been used in the plant, about 2100 kg a year during 1931-40 and about 650 kg a year during 1941-50. No asbestos fiber type is named.
• Main results:
  • Whole cohort, 1951-75: total deaths were close to expected (380 observed against 382.3 expected).
  • Whole cohort, 1951-75: 69 deaths from tumours against 76.7 expected.
  • Whole cohort, 1951-75: 5 deaths from tumours of the trachea, bronchus, lung and pleura against 7.2 expected.
  • Maintenance workers: 18 tumour deaths against 13.6 expected. The excess for employment of up to 14 years was statistically significant (p = 0.03).
  • Maintenance workers, incidence 1958-75: 4 tumours of the trachea, bronchus, lung and pleura were diagnosed against 1.0 expected (p = 0.038).
  • Of the 4 respiratory tumours among maintenance workers, two were pleural mesotheliomas. The time from first employment to diagnosis in these four cases ranged from 28 to 37 years.
  • Arc-furnace workers: one respiratory cancer case was a mesothelioma, in a man who worked at the plant from 1935 to 1946. Respiratory tumour incidence in this group was not increased (2 observed against 2.1 expected).
  • The authors judged that the mesotheliomas can probably be related to asbestos handling at the time the cases were induced.
  • Whole cohort, incidence 1958-75: stomach cancer was the only significant difference, and it was lower than expected (6 against 10.6 overall; 1 against 6.3 among men employed 15 years or more, p = 0.013).
  • Whole cohort, 1951-75: 48 deaths from accidents, poisoning and violence against about 36 expected, including 13 known suicides and 12 drownings.
• The authors' conclusion: The authors concluded that the study could not show an increased death rate or an increased cancer incidence in the plant population. They considered it reasonable to believe that the risk of respiratory tumours after inhaling trivalent chromium compounds is considerably less than after exposure to chromates.
• Limitations the authors state:
  • Chromium exposure levels were approximations, and no measured data existed for the period when an occupational cancer could have been induced.
  • No information on smoking habits was available, and smoking patterns may have differed between the workers and the mostly rural reference county.
  • The 15-year latency period used for all cancer sites was approximate.
  • The 95% confidence interval did not exclude a relative risk of 2.5 for lung cancer in this Swedish study.
  • The difference in the share of tumour deaths that were respiratory between 1931-50 and 1951-75 could not be evaluated, because no expected value could be calculated for the earlier period.

Topics

Medical terms in this study, explained in our Lexicon: Death Certificate, Cancer Registry, Mesothelioma, Asbestos Exposure.

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